全文获取类型
收费全文 | 547篇 |
免费 | 47篇 |
专业分类
测绘学 | 14篇 |
大气科学 | 37篇 |
地球物理 | 200篇 |
地质学 | 213篇 |
海洋学 | 7篇 |
天文学 | 82篇 |
综合类 | 10篇 |
自然地理 | 31篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 11篇 |
2020年 | 10篇 |
2019年 | 11篇 |
2018年 | 42篇 |
2017年 | 38篇 |
2016年 | 55篇 |
2015年 | 48篇 |
2014年 | 44篇 |
2013年 | 42篇 |
2012年 | 25篇 |
2011年 | 22篇 |
2010年 | 26篇 |
2009年 | 23篇 |
2008年 | 19篇 |
2007年 | 22篇 |
2006年 | 24篇 |
2005年 | 9篇 |
2004年 | 6篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 3篇 |
1998年 | 10篇 |
1997年 | 4篇 |
1996年 | 10篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 4篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1969年 | 2篇 |
排序方式: 共有594条查询结果,搜索用时 375 毫秒
541.
542.
Yu. N. Korenkov Carl W. Cable Vernon F. Cormier Vassily Levin Jacek A. Majorowicz Yehuda Bock Waclaw M. Zuberek Teng-fong Wong William L. Power Gary A. Robbins Piotr Raczka Krzysztof E. Haman Katarzyna Chałasinska-Macukow Ryszard Balcer Henryk Piwkowski 《Pure and Applied Geophysics》1991,137(3):309-336
543.
Sławomir Maj 《Physics and Chemistry of Minerals》1991,17(8):711-715
A relationship between the energy gap (E G) and the density (ρ) over mean atomic weight (〈A〉) ratio for Fe-poor oxide and silicate minerals is derived from simple properties of their free atom-components. Theoretical considerations are based on the Lorentz electron theory of solids. The eigenfrequency ν 0 of elementary electron oscillators, in energy units h ν 0, is identified with the energy gap of a solid. The numerical relation is of the form $$(\langle U_0 \rangle ^2 - E_G^2 )\frac{{\langle A\rangle }}{\rho } = \frac{4}{3}\pi \hbar ^2 \frac{{e^2 }}{m}N = 276.79 eV^2 cm^3 /mol$$ where 〈U 0〉 is the average first ionization potential (per free atom), ? is crossed Planck's constant, e is the electron charge, m is the electron rest mass, and N is Avogadro's number. For several geophysically interesting oxide and silicate minerals which are in general composed of four different elements (O, Si, Mg and Al), we obtain from laboratory data that the mean value of $$\left\langle {[\langle U_0 \rangle ^2 - (E_G^{lab} )^2 ]\frac{{\langle A\rangle }}{\rho }} \right\rangle \approx 248.2 \pm 20.9eV^2 cm^3 /mol.$$ . 相似文献
544.
Stanisław Kasperczuk 《Celestial Mechanics and Dynamical Astronomy》1995,63(3-4):245-253
The reduced Henon-Heiles system is investigated as a Hamiltonian dynamical system obtained by applying the normalization of the HamiltonianH=1/2(p
1
2
+p
2
2
+q
1
2
+q
2
2
)+1/3q
1
3
–q
1
q
2
2
to fourth-degree terms. The related equations of motion are bi-Hamiltonian and possess the Lie-Poisson structure. Each Lie-Poisson structure possesses an associated Casimir function. When reduced to level sets of these functions, the equations of motion take various symplectic forms. The various reductions give different coordinate representations of the solutions. These coordinate representations are used to seek the simplest representation of the solutions. 相似文献
545.
Witold Szczuciński Przemysław Niedzielski Lidia Kozak Marcin Frankowski Anetta Zioła Stanisław Lorenc 《Environmental Geology》2007,53(2):253-264
Study on contamination of tsunami sediments deposited on 26 December 2004 conducted shortly after the tsunami in coastal zone
of Thailand revealed elevated contents of salts in water-soluble and some heavy metals and arsenic in bioavailable fractions
(Szczuciński et al. in Env Geol 49:321–331, 2005). Few months later rainy season started and effected in total rainfall of over 3,300 mm. This paper presents results of survey
repeated 1 year after the tsunami. To assess the effects of rainy season on mobilization of previously determined potential
contaminants, the same locations were sampled again and analysed with the same methods. The tsunami deposit layer was well
preserved but in many locations the sediments were coarser than just after tsunami due to washing out of finer fractions.
The water-soluble salts contents were strongly reduced after the rainy season. However, the concentrations of acid leachable
heavy metals and metalloids were still elevated in comparison to reference sample from an area not impacted by tsunami. It
is possible that the metals and metalloids are successively moved to more bioavailable fraction from forms which were more
resistant to mobilization. 相似文献
546.
Artur Poręba Wacław M. Zuberek Jolanta Nogaj-Chachaj Andrzej Kotyrba Sławomir Siwek 《Acta Geophysica》2007,55(4):640-651
The aim of the research was to examine subsurface soil layers with the use of the Ground Penetrating Radar (GPR) method. Neolithic
archaeological post in Karmanowice was examined. On the basis of earlier geophysical researches and archaeological premises,
eight measurement profiles had been chosen. Ground Penetrating Radar system with antenna of 500 MHz frequency was applied.
The measurements were made with 30 and 60 ns time windows. The results were shown as the GPR sections. The analysis of the
obtained results allowed us to outline anomalies connected with the appearance of archaeological objects in subsurface soil
layers. The border between the anthropogenically changed upper layer and undisturbed loess was established, and the sections
of slope wash layers were designated. Anomalies were confirmed by digging and test drillings. Additionally, 2D resistivity
imaging method was used for verification of specific anthropogenic anomalies. 相似文献
547.
The authors present a method for estimation of interval velocities using the downward continuation of the wavefield to perform
layer-stripping migration velocity analysis. The generalized, phase-shift migration MG(F-K) in wavenumber-frequency domain
was used for fulltime downward extrapolation of the wavefield. Such downward depth extrapolation accounts for strong changes
of velocity in lateral and vertical directions and helps in correct positioning of the wavefield image in complex structures.
Determination of velocity is the recursive process which means that the wavefield on depth level z
n−1 (n = 0, 1, ...) is an input data-set for determination of velocity on level z
n
. The velocity ν [x, z
n
− z
n−1] can be thus treated as interval velocity in Δz
n
= z
n
− z
n−1 step. This method was tested on synthetic Marmousi data-set and showed satisfactory results for complex, inhomogeneous media. 相似文献
548.
Karol Kuliński Joanna Święta-Musznicka Andrzej Staniszewski Janusz Pempkowiak Małgorzata Latałowa 《Journal of Paleolimnology》2007,38(4):555-567
The quantity and quality of lignin phenols (Σ8, Λ, S/V, C/V and (Ad/Al)v) in the sediments of three small Lobelia lakes with neither inlets nor outlets were investigated and compared with palynological data and lithology of the profiles.
The method of alkaline CuO oxidation was used. Substantial differences with respect to sedimentary lignin concentration and
provenance recorded along the profiles and among the sites are in good agreement with pollen data describing the dominant
type of vegetation and with indices of soil erosion in the lakes’ catchments. This relation shows that the compositions of
lignin degradation products in these lakes are closely related to the local environmental conditions. In all the lakes gymnosperm
wood is the main source of lignin products; however, each lake is characterized by different S/V index values. Especially
good correlations were obtained between pine pollen proportions in sediments and the S/V index. The correlation between the
C/V and (Ad/Al)v indices indicates a higher degradation of organic matter when non-woody tissue is more abundant. This pilot study illustrates
the usefulness and potential for a wider application of lignin oxidation products in palaeoecological reconstructions. This
kind of data would be of special importance when investigating local presence/absence of woody plants and the role of angiosperms/gymnosperms
in local vegetation. Estimates of lignin biodegradation levels, as well as the data on diagenetic processes, may afford supplementary
information on possible disturbances in sedimentation. 相似文献
549.
Agnieszka Gałuszka 《Environmental Geology》2007,52(5):861-870
One of the most crucial issues of recent environmental sciences is the topic of background concentrations of elements and
organic compounds in various abiotic and biotic systems. The relationship between natural and anthropogenically altered concentrations
of chemical species is a question that involves many implications in the geosciences, environmental and biological sciences,
toxicology, and other related disciplines. This is especially important when interpreting geochemical and biogeochemical anomalies
of toxic elements and/or organic compounds in various media. To better understand the potential impact of hazardous substances
in the environment, we must become more familiar with their spatial and temporal distribution and with their behavior under
different physico-chemical and biotic conditions. This review presents an assessment of the geochemical background concept
as used by various authors. Different assumptions and approaches to this topic are presented, including direct, statistical,
and integrated methods. Based on the results derived from geochemical and biogeochemical studies performed in selected forest
ecosystems of Poland, an integrated method is presented. As a consequence of data processing, a normal distribution of data
points was obtained using an iterative 2σ-technique. This method of estimating geochemical background is feasible and can
be used for setting environmental quality standards or for studying the impact of anthropogenic pollution sources on the environment. 相似文献
550.